1. Field of the Invention
The present invention relates to an image forming apparatus with an electrophotographic system that forms an image by developing an electrostatic latent image formed by scanning a plurality of photoconductors with a plurality of light beams.
2. Description of the Related Art
An image forming apparatus with an electrophotographic system forms an image by exposing a photoconductor with a laser beam (light beam) and by developing an electrostatic latent image formed on the photoconductor. The laser beam emitted from a light source (Laser Diode: LD) is deflected by a rotation polygon mirror so that the laser beam concerned scans the photoconductor. The laser beam deflected by the rotation polygon mirror is guided to the photoconductor through optical elements, such as lenses and mirrors. Japanese Laid-Open Patent Publication (Kokai) No. 2006-297755 (JP 2006-297755A) discloses a color image forming apparatus equipped with a photoconductor, an LD, and a rotation polygon mirror for each color. This publication discloses the image forming apparatus that corrects a deviation between toner images formed on the respective photoconductors by controlling rotation phases of the rotation polygon mirrors.
In an image forming apparatus with the electrophotographic system, a timing at which light quantity of a laser beam is controlled and an emission timing of a laser beam according to an image signal are controlled by a laser driver. The laser drivers are mounted on light sources of respective colors.
The technique of JP 2006-297755A controls the rotation phases so that a predetermined phase difference occurs among the rotation phases of the rotation polygon mirrors. Accordingly, such an image forming apparatus that is described in this publication controls laser drivers so that timings at which light quantity of laser beams are controlled and emission timings of the laser beams according to image signals differ for the respective LDs.
On the other hand, there is a known image forming apparatus that deflects laser beams emitted from light sources (LDs) corresponding to photoconductors with one rotation polygon mirror in order to miniaturize an optical system.
However, such an image forming apparatus cannot control the LDs easily when timings at which light quantity of laser beams are controlled and emission timings of the laser beams according to image signals differ for the respective LDs.